Nonlubricated formed gearing



Feb. 21, 1967 FIG. 7

TTTTTT EY United States Patent Oiilce 3,304,795 Patented Feb. 21, 19613,304,795 NONLUBRICATED FORMED GEARING William S. Rouverol, 2120 HasteSt., Berkeley, Calif. 94704 Continuation of application Ser. No.336,231, Jan. 7, 1964. This application Feb. 28, 1966, Ser. No. 534,5789 Claims. (Cl. 74-411) This is a continuation of application Ser. No.336,231, tiled Jan. 7, 1964, now abandoned.

This invention relates to nonlubricated formed gearing of the typedisclosed in United States Patent No. 3,169,- 408. The instant inventionrelates when the transmitting As 4a result of this deformation the toothpitch for certain portions of the driving and siderable wear. Only -byreducing the transmitted can this be prevented and reduction of torqueof correspondingly reduces the power capacity.

e main object of the present invention is, therefore, to provide aconstruction torque course forms which the present intively soft rubberor other elastomer having similar characteristics. Secured to the outerperiphery of the backing ring 2 is a rim member 3 which, as shown inFIG. 1, is relatively thin in radial extent but of suicient thickness tobe formed with gear teeth 4 and still retain a thin section 5 betweenthe root circle of the teeth and the outer periphery of the backing ring2. In the case tooth profile sections of gears1 zoy - vention.

of ,an internal gear the above described parts will o1 course bereversed in a radial direction.

Soft nylon is a preferred material for the rim 3 but other plastics mayalso 'be employed. The modulus oi the elasticity of the material formingrim 3 should be be tween 30,000 and 50,000 lbs/sq. in. although somehigh strength plastics with moduli of 100,00 to 200,000 lbs/sq. in.might Work depending upon the other dimensions and under a given load.

Assuming the modulus of elasticity of the rim 3 to be substantiallygreater than the modulus of elasticity of the backing ring 2 it undergobending in connection with such radial inward deformation because of therelatively thin section 5. Furthermore, since the modulus of elasticityof the backing ring 2 is relatively low, the yieldability of `backingring 2 will .also permit the relatively large radial deformation abovenoted.

The important consequence of the above described struct-ure is thatthere is less likelihood of a change in rim 9 has a relatively highrigidity.

It will fbe noted that the gear teeth in FIGS. l and 2 are shownsomewhat elongated in a circumferential direction compared to theirradial height.` Although lthis construction is preferable, otherconstructions of the teeth are possible without plurality of throughopenings 16 extending 'between 0pposite sides of the gear.

Between the inner portion of from the scope of this ing' 3 with theopenings 16 and the he lrim which is provided gear teeth 18 there -isprovided a solid continuous ring 17 which may be relatively thin inradial extent. The teeth 18 are also provided with through openings 19extending between opposite sides of the gear so as to reduce therigidity of the struct-ure in a radial direction and at the same timeretain relatively higher rigidity in a tangential direction. In lieu ofmoderately hard rubber in the structure of FIG. 3 a soft nylon may .beemployed, the important consideration being that rigidity be built in tothe structure in a tangential direction to a greater degree than in aradial direction.

T-he advantages of the invention may also be obtained by substituting arelatively thin steel rim in lieu of the nylon above described. In thiscase, as shown in FIG. 4, the backing ring 20 is formed substantially tothe shape of the completed gear but there is integrally molded therewitha thin ribbon of steel 21 so that metal-to-metal engagement is presentwhen the teeth are running. In this case it will be apparent thatcircumferential rigidity is achieved through the relatively high-modulus of elasticity of steel and at the same time radial deformationis permitted because the backing ring 20, made of rubber or similarelastomer, has relatively low resistance to deformation in a radialdirection.

The -result obtained by the structures of FIGS. l and 2 may also be`achieved as shown in FIG. by the provision of a plurality of axiallyspaced wire hoops 25 of steel or the like interposed between the gearteeth and the backing ring. In this case the backing ring and teeth aremolded as a unit from rubber or soft nylon and in the molding processthe hoops 25 are inserted so as to withstand the tangential loading. Itwill be noted in FIG. 5 that the hoops 25 are spaced slightly inwardlyfrom the roots of the teeth '26 so as to provide a relatively thinsection 27 between said roots and said hoops 25.

A similar simplified manufacture may be effected by incorporating aconventional timing belt in the gear construction as seen in FIG. 6. Inthis case the usual backing ring 30 is provided to which is lixedlysecured as by adhesive a conventional timing belt generally designated31. Although the rim structure may, of course, be readily manufacturedfor this special purpose, it is possible to use a conventional timingbelt such as, for example, the type available under the trademark GilmenSince such timing belts are employed with the teeth directed inwardly,all that is requi-red is to turn the timing belt inside out so that theteeth are directed outwardly and secure the same to the rubber backingring 30.

Said timing belt or its equivalent includes an inner layer of fabric 32to which is integrally secured a rubber rim portion 33 covered with a.nylon facing 34. The nylon facing 34 is relatively thin but has goodwearing qualities and is permitted to yield inwardly against theinherent yieldability of the rubber 33 and the rubber ring 30. By thisconstruction the general objects of the invention are achieved, that is,the radial rigidity of the assembly is considerably less than thetangential rigidity so that the desired radial deformation may takeplace without the tangential deformation becoming so large as to resultin one tooth climbing on its mating tooth.

It has been found that gears manufactured in accordance with the presentinvention are able to transmit an amount of power commensurate with thattransmitted by metal gears of similar size because of the fact thatseveral teeth 'contribute to transmitting the torque and the unusuallyhigh bearing stress associated with conventional metal gears is notpresent. Furthermore, the heat dissipation in the gears of the instantinvent-ion is extremely good and the noise level is considerably belowthat of conventional metal gearing.

The very specific description given above of the preferred forms of theinvention is not to be taken as restrictive since it will be apparent tothose skilled in the art that various modifications of design nature maybe resorted to without departing from the scope of the following claims.

I claim:

1. A gear including an elastomer toothed rim,

the teeth of said rim including axially extending openings to reduce theresistance to bending of said teeth under load applied to said teeth ina radial direction.

2. A gear construction that includes a pair of mating gears eachprovided with .a power transmitting rim,

the rim of each of said gears comprising a toothed ring of yieldablematerial and a backing ring of yieldable material on the side of saidtoothed ring opposite the mating gear,

said rim providing substantially less rigidity in a radial directionthan in a tangental direction.

3. Gear construction according to claim 2 wherein said toothed ring isreadily deformable in a radial direction under loading by the matinggear and being relatively rigid in .a tangential direction.

4. Gear construction according to claim 2 wherein said toothed `ring issupported only on said backing ring and said backing ring is supportedon a rigid hub, and wherein radial deformation of said rim under loadingby the mating gear is resisted only by said toothed ring, backing ringand hub.

5. Gear construction .according to claim 2 wherein said backing ring isof substantially greater radial extent than said toothed ring.

6. A gear construction that includes a pair of mating gears, each ofsaid gears comprising:

a rigid hub,

a power transmitting rim fixed to said hub and comprising a toothed ringof yieldable material and a backing ring of yieldable materialinterposed between said toothed ring and said hub,

said backing ring being of a material having a substantially lowermodulus of elasticity than the material of said toothed ring wherebysaid ring deforms in a radial direction under loading to a substantiallygreater extent than in a tangential direction.

7. A gear construction .according to claim 6 wherein a eircumferentiallyextending tension member is interposed between said toothed ring andsaid hub.

8. A gear construction according to claim 7 wherein said tension memberis a continuous hoop of relatively high modulus of elasticity.

9. A gear construction `according to claim 7 wherein said tension memberis of a fabric.

References Cited bythe Examiner UNITED STATES PATENTS 820,789 5/1906Hutchins 74F460 2,753,731 7/1956 McWethy 74-443 3,078,206 2/1963 Skura74-231 X 3,216,267 11/1965 Dolza 74-411 X DAVID I WILLIAMOWSKY, PrimaryExaminer, Lj HT GERIN, Assistant Examiner:

2. A GEAR CONSTRUCTION THAT INCLUDES A PAIR OF MATING GEARS EACHPROVIDED WITH A POWER TRANSMITTING RIM, THE RIM OF EACH OF SAID GEARSCOMPRISING A TOOTHED RING OF YIELDABLE MATERIAL AND A BACKING RING OFYIELDABLE MATERIAL ON THE SIDE OF SAID TOOTHED RING OPPOSITE THE MATINGGEAR, SAID RIM PROVIDING SUBSTANTIALLY LESS RIGIDITY IN A RADIALDIRECTION THAN IN A TANGENTAL DIRECTION.